When looking at a map this is a strange extension of Namibia running east between Angola and Botswana, only about 50 km wide.
The "Caprivi Strip." a.k.a Okavango Panhandle, etc. Created to give Namibia (then German West Africa) access to the Zambezi River.
Anyway - I'm waiting for the data. I can imagine numerous scenarios that account for the rapid descent and lack of radio transmissions as reported so far. But without further detail they are just possibilities, not probabilities.
And I'm willing to wait. Absent an obviously identifiable and imminent threat to other aircraft and crews, I don't see a lot of value in handling investigations as "data dumps" into the social-mediasphere.